Heretofore known in the art is a technique of estimating whether or not a moving object crossing a pedestrian crosswalk and a subject vehicle come close to each other (e.g. WO2011/086661).
The prior art is, however, to detect only a moving object crossing a pedestrian crosswalk located ahead of the subject vehicle, that is, a moving object observed before the subject vehicle gets across the pedestrian crosswalk. The problem is therefore that a moving object that may come close to the subject vehicle when the subject vehicle approaches a pedestrian crosswalk cannot be detected before the subject vehicle comes close to the pedestrian crosswalk.